ᐅ Natural stone wall/bed instead of planting rings – What do you recommend?

Hello, I’m curious to hear your opinions and advice.
In the garden, our previous owner has currently built a full retaining wall towards the neighboring property using those awful red planting rings. There are up to 5 rows in total (so probably just under 1.5 meters (5 feet) high).
In short: they have to go… Everything inside dries out, there’s no flowerbed, and so on.
My idea is to remove everything and build two natural stone walls with a bed in between (so: lawn – wall – 75 cm (30 inches) bed – wall – 75 cm (30 inches)). The wall would also be planted in a wild and bee-friendly way. The entire length would be just under 20 meters (65 feet). What do you think this would cost if a) I do it myself or b) have a gardener do it?
For option b), we will receive an estimate in about 3 weeks, but unfortunately I have no idea what to expect cost-wise.

Best regards

For us, only 10 m (about 33 feet), approximately 1 m (3 feet) high, labor including excavator 2500 net. Material 800, total 3300 plus tax.

Thank you for your response. Does that include the concrete foundation? And do you have any photos of the result? Best regards and have a great weekend.

@Nordlys you more or less got the stones for free, from a cemetery or somewhere else?

Normally, 1 ton costs around 80-100 euros, which is about 1 meter (3.3 feet) of a 50x50cm (20x20 inches) block.

Labor costs are about right, though usually higher depending on the region.

You can roughly calculate the rest yourself.

I paid 15 each for the stones at the cemetery administration. And there were enough of them to total around 800.

The requested photo.